Antigen receptor engagement selectively induces macrophage inflammatory protein-1 alpha (MIP-1 alpha) and MIP-1 beta chemokine production in human B cells

We show herein that B cell Ag receptor (BCR) triggering, but not stimulation by CD40 mAb and/or IL-4, rapidly induced the coordinated expression of two closely related T cell chemoattractants, macrophage inflammatory protein-1 beta (MIP-1 beta) and MIP-1 alpha, by human B cells. Naive, memory, and germinal center B cells all produced MIP-1 alpha/beta in response to BCR triggering. In contrast to MIP-1 alpha/beta, IL-8, which is spontaneously produced by germinal center B cells but not by naive and memory B cells, was not regulated by BCR triggering. Culturing follicular dendritic cell-like HK cells with activated B cells did not regulate MIP-1 alpha/beta production, but it did induce production of IL-8 by HK cells. Microchemotaxis assays showed that CD4+CD45RO+ T cells of the effector/helper phenotype actively migrated along a chemotactic gradient formed by BCR-stimulated B cells. This effect was partially blocked by anti-MIP-1 beta and anti-CC chemokine receptor 5 Ab, but not by anti-MIP-1 alpha Ab suggesting that MIP-1 beta plays a major role in this chemoattraction. Since maturation of the B cell response to a peptide Ag is mostly dependent on the availability of T cell help, the ability of Ag-stimulated B cells to recruit T cells via MIP-1 alpha/beta, may represent one possible mechanism enabling cognate interactions between rare in vivo Ag-specific T and B cells.